Thanks for the advice. I will have a play around with gimp!
You have one of the best graphic sets around! Why not do a YouTube tutorial for beginners?
Thanks, but if anything I'll write up a tutorial with a few images instead of a video. Though I'm a little too busy to invest time into writing an extensive tutorial at the moment. And I don't think I'm that well versed in DF graphics. There are people much more experienced than me.
Oh another thing I forgot to mention, you should be aware that there is a "hierarchy" or two "layers" when talking about DF visuals (or visuals of similar games):
One is recognizing single tiles of course, which is straightforward to achieve.
Before that, however, you have to recognize the "structure", or "organization" of the scene presented. In other words, you should be able to see at first glance how the rooms are divided, what stockpiles are and where there's only floor. You should be able to differentiate between the current z-level, the one below, and ones even further below easily.
Kind of when you would zoom out, you should still be able to make out rooms, geography, and so on.
Even further, if possible, being able to discern creatures from items/floors helps with playing, too.
The most important thing to consider in that regard is that you should make sure walls are very different from floors (both smooth and engraved), Floors should be rather unobtrusive, low-key, walls should be easily to identify. and vegetation blends in with grass without becoming invisible. In ASCII-like tilesets, the mass of black with all the tiny punctuation in the middle can make it harder to identify things because it clutters up the view and everything seems to blend together. Though the walls usually stick out fine. With very detailed tilesets, on the other hand it might happen that the walls drown amongst the other tiles (although the three "big" graphic sets Ironhand, Mayday, and Phoebus don't have that problem).